Existing multi-speed transmissions include gearshifting arrangements where the gearshifting force required is partly or wholly supplied by the vehicle's own source of energy. They have the disadvantages that no simple control of the gearshifting force is possible (especially pneumatically) and that relatively expensive parts are needed. Sources of energy likewise are not available in all vehicles wherefore they must be additionally installed when required.
An electric power supply, which performs a multiplicity of tasks in a vehicle, offers itself as a source of energy present in any vehicle. A modification for the purpose of electronic control is therefore relatively easily performed. The trend in modern vehicles is toward electronic control of vehicle functions (for instance, automatic transmission, injection and ignition systems, ASC). It appears important to supply the same energy to the control range and the power range. In an electrically actuated transmission, this means that an unnecessary change in the kind of energy used in the system for shift control to a different kind of energy for production of shifting force is avoided. Advantages are to be seen, for instance, in the travel and time-dependent control of the shifting force.
Such gearshifting arrangements are known in many different designs. But common to all is that they use, a separate electric motor for activation of each gearshifting set, with the result being a relatively complex construction coupled with the need of a comparatively large space.
Thus, U.S. Pat. Nos. 2,462,779 and 2,754,692 show a transmission control where an electric motor, having a ball threaded spindle (spatial transmission) secured to its shaft, is associated with each gearshifting lever which interacts with a relatively complex angular lever-spiral spring system. Consequently, three electric motors with three motion-transmitting devices are situated in a six-speed transmission with the result, especially in the latter, of a relatively multi-part, complex construction with great complexity and that demands a relatively large space.
Gearshifting arrangements in which worm drives are used are also known. On the respective electric motor associated with a gearshifting lever, a worm is situated, substantially coaxially with the motor shaft or secured thereto, which interacts with a worm gear and a complex lever system. Austrian patent 262,791 shows a worm drive interacting with a crank drive which, in turn, moves the gearshifting lever. In the gearshifting arrangement of EP-AZ O 198 111, the worm gear interacts with a rack which is substantially parallel to the axis of the transmission wheels and, in turn, actuates the gearshifting lever via a lever-spring system.
In addition, there are known gearshifting arrangements which use electric motors combined with cam discs, and a stepdown gear that is situated between the motor and the cam disc or cam. GB-A 2097077 shows a gearshifting arrangement wherein the cam actuates a sliding device that runs against spring tension and moves the end of the gearshifting lever provided with a ball. DE-OS 28 06 907 shows a gearshifting arrangement which is provided with a cam disc provided with cams on the front side. Sliding blocks are moved via dogs by means of a guide roller combined with an auxiliary lever, an actuating lever and crank arms.
The problem to be solved by this invention is to provide a gearshifting arrangement, of the above kind, having an economic structure, manufacture and assembly (that is, simple, reliable and space-saving).